Many vehicles engaged in the distribution of foodstuffs maintain refrigeration of the vehicle by means of eutectic plates. Essentially these are metal tanks filled with a eutectic, which is a mixture which freezes or melts at a constant temperature, those in use normally being operated at between about minus 20.degree. C. and 0.degree. C. to cover chilled and frozen foods. The vehicles utilizing these plates are typically well insulated and the plates will maintain the interior of the vehicle at the proper temperature for several hours. After this time, the plates are re-frozen by circulating a refrigerant such as a mixture of chilled brine through pipes which form part of the structure of the tank. The refrigerant itself is refrigerated from a central refrigerator often situated in a vehicle depot. This freezing process can take several hours and, as mechanical refrigerators are often used, noise can be a significant problem.
The present invention seeks to address these problems and to provide improved simplicity, speed and quietness of the recharging step by substituting a liquid cryogen, such as liquid nitrogen, for the conventional mechanical refrigeration apparatus necessary to circulate a refrigerant such as brine.